1. Field of the Invention
The present invention relates to a flow channel switching valve for use in, for example, an auto-sampler that introduces a sample to an analysis flow channel of a liquid chromatograph.
2. Description of the Related Art
As an example, in an auto-sampler that introduces a sample to an analysis flow channel of a liquid chromatograph, after the sample is taken into a sample loop from a sample container, the sample loop is connected to an upstream side of a separation column in the analysis flow channel by switching of a flow channel switching valve, which allows the sample in the sample loop to be transported to a separation column side by a mobile phase flowing in the analysis flow channel.
As the flow channel switching valve for use in the liquid chromatograph, a rotary type switching valve is common. The rotary type switching valve switches a connected flow channel by rotating a rotor (rotary part) (e.g., refer to Unexamined Japanese Patent Publication No. 2008-215494).
In the rotary type switching valve, a plurality of connection ports for connecting flow channel piping are provided in an upper portion of a housing, and a rotor and a stator (stationary part) are contained inside the housing. The rotor and the stator are in contact with each other in a state where planes thereof keep liquid tightness with each other, and the stator is fixed by a pin or the like so as not to rotate with respect to the housing. The connection ports communicate with the rotor through flow channels provided in the housing and holes of the stator. A groove forming a flow channel connecting between the connection ports is provided in a surface on a stator side of the rotor, and driving and rotating the rotor while sliding on the stator changes a position of the groove, thereby switching connection between the connection ports.
Since the rotor and stator of the flow channel switching valve are consumable stores that slide and are worn away by the rotation of the rotor, they need to be exchanged as needed. In the housing containing the rotor and the stator, the upper portion (hereinafter, a housing top) of the housing provided with the connection ports is detachable from a body of the housing (hereinafter, a housing body), and the exchange of parts such as the rotor, the stator and the like is performed in a state where the housing top is detached from the housing body.
It is common to sandwich a packing between the stator and an inner wall surface of the housing top and thereby keep the liquid tightness. Since holes leading the connection ports in the housing top to the plane of the rotor are provided in the stator and the packing, the stator, the packing and the inner wall surface of the housing top need to be precisely positioned. Thus, when the housing top is attached to the housing body, it is necessary to mount the housing top on the housing body after attaching the stator and the packing to a housing top side. In order to prevent the stator and the packing from dropping from the housing top when attaching the housing top to the housing body, it is common to fix the stator and the packing to the housing top by a spring pin or the like.
However, since fixing the stator and the packing to the housing top by the spring pin or the like makes it difficult to detach the stator and the packing from the housing top, in many cases, when the stator is exchanged, the whole housing top is exchanged in place of exchanging only the stator. This increases exchange costs of parts.
Moreover, in the case where the stator and the packing are not fixed to the housing top by the spring pin or the like, a worker needs to be careful not to drop the stator and the packing from the housing top, which is not easy work for the worker.